Studies concerned with the structure and function of RNA polymerase will be continued. These will include studies on RNA DNA covalent hybrid formation. The biological role, if any, of RNA ligase will be examined in various amber mutants. The nature of the RNA substrate in this reaction will be examined. DNA replication and the role of various dna genes of E. coli will be pursued. Studies on the replication of RNA tumor viral RNA will be studied in vitro.